Cambridge, Mass., March 9, 2017 - Mersana Therapeutics, Inc., a clinical-stage biotechnology company focused on discovering and developing a pipeline of antibody drug conjugates (ADCs) based on its proprietary Fleximer® technology, today announced that it was awarded EP Patent No. 2717916 B1, entitled “Protein-Polymer-Drug Conjugates.”  This patent provides Mersana comprehensive coverage in the European Union for its polymer-based Fleximer-ADC platform technology.  The patent covers Fleximer-antibody drug conjugates and their methods of use as well as Fleximer-drug conjugates that can be linked to an antibody or antibody alternative to create next-generation antibody drug conjugates.  The patent also has claims directed to Mersana’s proprietary auristatin payload.

"Mersana’s latest patent grant is an important addition to our current ADC intellectual property portfolio and strengthens the patent position for our Fleximer conjugation technology platform,” said Anna Protopapas, President and CEO of Mersana Therapeutics. "Issuance of this patent provides comprehensive intellectual property protection in the European Union for our ADC technology for our internal pipeline as well as our partners’ programs by covering proprietary payloads, Fleximer polymer linker technology, and conjugation to antibodies or antibody alternatives."

About Fleximer Antibody-Drug Conjugate Technology

Mersana’s next-generation Fleximer antibody-drug conjugate (ADC) technology, as exemplified by our lead platform Dolaflexin®, is based on the Company’s proprietary ADC technology using a biodegradable polymer, known as Fleximer, and a wide variety of linkers that allow for the attachment of an extensive range of anti-tumor payloads to the Fleximer polymer. Once loaded with the payload drug(s), Fleximer can then be attached, through a linker that is different from the drug linkers, to an antibody or antibody alternative to create a Fleximer-ADC. Mersana’s novel linker systems are designed to be stable in the bloodstream and release the potent payloads once inside the targeted cancer cell. Mersana’s Fleximer-ADC technology provides several key advantages over currently available approaches, including: ability to deliver diverse payloads; opportunity to significantly increase drug loading per antibody; the potential to increase efficacy and tolerability; the potential use with antibody fragments and alternative targeting moieties in addition to monoclonal antibodies and ability to optimize the size of the drug conjugate to efficiently perfuse solid tumors while controlling the half-life of the resulting conjugate in circulation. Mersana’s most advanced Fleximer-based platform, Dolaflexin, delivers a proprietary auristatin payload with unique time-dependent metabolism that in preclinical models has shown the potential to maximize anti-tumor efficacy while mitigating systemic toxicities related to recirculation of free drug payload out of the tumor.

About Mersana Therapeutics                                      

Mersana Therapeutics is a clinical-stage biotechnology company with highly differentiated and proprietary antibody drug conjugate platforms that allow for significantly higher drug loads, and potentially providing greater efficacy while simultaneously increasing tolerability. As a result, our platforms create expanded opportunities to deliver meaningful clinical benefit to patients.  Our lead product candidate, XMT-1522, is in Phase 1 clinical trials. We expect that our second product candidate, XMT-1536, will be entering clinical development in early 2018.  In addition, our partners are advancing their pipeline of antibody drug conjugates using our platforms.

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